Keywords: adsorption, degradation, dissolution, remobilisation, speciation, wastewater effluents, dairy industry, waste management, ethylenediaminetetraacetic acid, EDTA acid, trace metals, environmental pollution, dairy effluents
EDTA in the environment: with special reference to the dairy industry
Ethylenediaminetetraacetic (EDTA) acid has been used as an additive to caustic agents facilitating removal of Ca, Mg and trace metals in dairy processing plants for many years. Effluents from the dairy industry are either discharged to surface waters or used in land irrigation systems. In particular, the effluents from a large dairy factory discharged to a small stream have the potential to pose an environmental risk. Long-term irrigation of dairy effluents can induce changes in the quality of soils, or may induce a risk of groundwater contamination. This paper reviews the interactions of EDTA chelates and metals upon release to the environment, which determines the speciation of EDTA relating to its potential environmental risk. The alkaline earth metal chelates (Ca, Mg, etc.) are the key factor in the speciation of EDTA in the dairy industry. The concentration of EDTA and the speciation of EDTA from dairy effluents are of some potential concerns.